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In a nutshell for the benefit of lay visitors, the gas fire is set working on full flame, with doors and windows tight shut. A smoke match is then introduced under the draught diverter at e on the sketch. That is to say under the open base of the draught diverter. For the record this test is also carried out under additional challenging conditions known to RGI. That includes testing with any fans working in the same or an adjacent room.
If the products of combustion (POC) are being evacuated efficiently up the flue, the smoke introduced at e will be pulled into the draught diverter, as if by a vacuum cleaner. If the flue fails to clear POC, the smoke from the smoke match will 'spill' into the room and choke the RGI, hence the expression spillage test.
Carrying out the spillage test at the base of draught diverters is well known to RGI and commonplace on open-flue boilers. Principle old as gas itself. However this represents a profound shift from the spillage test shown in the original MI. Nothing wrong with that in theory but we have to ask why the change. The spillage test position on gas fires traditionally, has always been (and still is) carried out at the front of the gas fire, as shown in the original MI. |